Energy and momentum dependence of nuclear short-range correlations - Spectral function, exclusive scattering experiments and the contact formalism

TL;DR

This paper investigates how nuclear short-range correlations influence electron-induced knockout reactions, deriving a relation between spectral functions and nuclear contacts, and analyzing experimental data to understand the dependence on energy, momentum, and nucleon-nucleon interactions.

Contribution

The study introduces a formalism linking spectral functions to nuclear contacts and applies it to analyze experimental data, revealing potential to constrain nuclear potentials.

Findings

The ratio of proton-proton to proton-neutron pairs depends mainly on a single contact ratio.

A deep minimum in the contact ratio is associated with the node in the proton-proton wave function.

Spectral functions show sensitivity to nucleon-nucleon interactions, offering a way to constrain nuclear potentials.

Abstract

Results of electron-induced one- and two-nucleon hard knockout reactions, $A(e,e'p)$ and $A(e,e'pN)$, in kinematics sensitive to nuclear short-range correlations, are studied using the nuclear contact formalism. A relation between the spectral function and the nuclear contacts is derived and used to analyze the dependence of the data on the initial energy and momentum of the knocked-out proton. The ratio between the number of emitted proton-proton pairs and proton-neutron pairs is shown to depend predominantly on a single ratio of contacts. This ratio is expected to present a deep minima in the initial energy and momentum plane, associated with the node in the proton-proton wave function. The formalism is applied to analyze data from recent $^4$He and $^{12}$C electron-scattering experiments performed at Jefferson laboratory. Different nucleon-nucleon potentials were used to asses the model-dependence of the results. For the ratio of proton-proton to proton-neutron pairs in $^4$He, a fair agreement with the experimental data is obtained using the two potentials, whereas for the ratio of proton-proton pairs to the total knocked-out protons in $^{12}$C, some of the features of the theory are not seen in the experimental data. Several possible explanations for this disagreement are discussed. It is also observed that the spectral function at specific domains of the momentum-energy plane is sensitive to the nucleon-nucleon interaction. Based on this sensitivity, it might be possible to constrain the short range part of the nuclear potential using such experimental data.